An internal combustion engine of a self propelled vehicle or machine needs to be provided with clean air for the combustion process. Especially if the vehicle or machine is used in an agricultural harvesting environment, where the ambient air contains large amounts of dust and plant material being generated from the harvesting machinery, an efficient air precleaning and filter arrangement is required. For a combine harvester, this is in the prior art generally done with a single large cyclone precleaner and a porous filter downstream the cyclone precleaner to provide the final stage of filtering needed for the engine combustion air.
The cyclone precleaner, also named vortex-type filter, comprises a vortex generating inlet passage and a cooperating outlet passage. Both passages may be cylindrical or somewhat conical, and are axially aligned to each other. The entrance of the outlet passage is smaller than the exit of the inlet passage and located proximate to the exit of the inlet passage. The passages extend within a filtration chamber that is separated from the entrance of the inlet passage and the exit of the outlet passage. From this filtration chamber, the separated material is drawn by an external source through an aspiration port, also named scavenge port.
In operation, unfiltered fluid enters the inlet passage, where a vortex motion is imparted in the fluid flow. The heavier material in the flow, be it fluid or debris, is thrown radially outward toward the inlet passage walls by the centrifugal force of the vortex motion. Thus, the flow is separated into a lighter portion at the center of the inlet passage and a heavier portion near the wall of the inlet passage. As the fluid exits the inlet passage, the heavier separated portion flows past the entrance of the smaller outlet passage and into the filtration chamber, while the lighter filtered portion enters and flows through the outlet passage. The material from the filtration chamber is drawn through the scavenge port into exhaust flow of the engine.
A problem with this precleaner arrangement is that the single large cyclone filter is in a number of cases not efficient enough to pre-filter enough of the dust out of the air stream. This results in heavy dust loading on the air filter element. The life of this filter element is thus reduced and when the filter gets plugged, the air flow to the engine is restricted and the engine loses power. The filter then either needs to be replaced with a new one or blown out with compressed air, what is a time-consuming and filthy task. In some crops and conditions, the filter needs to be serviced in this way as often as once per day. This is unacceptable to most users.
In DE 103 36 206 A, it was proposed to use a block containing a number of cyclone precleaners arranged in parallel, whereby two such blocks are arranged in series upstream and downstream a turbocharger, for precleaning combustion air for an engine of an agricultural vehicle. This document does not disclose how the scavenge ports of the cyclone filters are aspirated.
Thus, there is a need for a precleaner arrangement for an internal combustion engine providing an efficient precleaning effect.
It is an object of the present invention to provide an effective precleaner arrangement for an internal combustion engine.